This invention relates broadly to double action fastener installation tools.
The pertinent prior art is indicated by VanHecke U.S. Pat. No. 2,820,566 and the technical brochure of the Huck Manufacturing Company, entitled, "Instruction Manual, Model 200 Installation Tool," copyrighted under notice 1965, 1975. Both of these disclosures are incorporated herein by reference.
The present application is also related to application Ser. No. 564,078 filed Apr. 1, 1975, and assigned to Huck Manufacturing Company, such application having been abandoned.
The primary object of the present invention is to assure the proper functioning of a double action installation tool by the incorporation of an improved shift valve mechanism so constructed and associated with the oil pressure circuit as to prevent premature actuation of the shift piston .